The present invention relates to a multilayered thin film element and, more particularly, to a thin film element with an uppermost protective film of a novel structure.
In a thin film element in which thin films are deposited on a substrate, a protective film is formed as the uppermost layer to protect the underlying thin films. In some thin film elements, the substrate is cut into chips each of which is abraded. Therefore, the protective film directly affects the reliability of the thin film element.
The protective film is conventionally often made of a relatively thick single insulator with relatively high hardness. Meanwhile, a heat-resistant photoresist organic material has been recently used as the insulating interlayer. The photoresist film has been used because the photolithography techniques such as exposure and development can be performed to etch a relatively thick layer without the conventional etching process and because step coverage of a high step is excellent due to its viscosity. However, still presented are the problems such as the internal stress and adhesion strength of the protective film and the step coverage at the edges of high steps. If these problems occur, a protective film 9 peels off from the edges of the high step portion immediately after it is formed. Even if the protective film 9 does not peel off immediately after it is formed, the protective film 9 together with a thin film formed thereunder may peel off or float when the thin film element is cut into chips or processed. Further, when an organic material is used for the insulating interlayer, the temperature range is limited so that an excellent protective film can hardly be formed.